# std::atomic_flag_notify_all

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< cpp‎ | atomic

Defined in header `<atomic>` |  |
void atomic_flag_notify_all( std::atomic_flag* object ) noexcept; | (1) | (since C++20)
void atomic_flag_notify_all( volatile std::atomic_flag* object ) noexcept; | (2) | (since C++20)

Performs atomic notifying operations.

Unblocks all threads blocked in atomic waiting operations (i.e. std::atomic_flag_wait(), std::atomic_flag_wait_explicit(), or `std::atomic_flag::wait()`) on *object, if there are any; otherwise does nothing.

Equivalent to object->notify_all().

### Parameters

object | - | pointer to the `atomic_flag` object to notify

### Return value

(none)

### Notes

This form of change-detection is often more efficient than simple polling or pure spinlocks.

### Example

| This section is incomplete Reason: no example

### See also

notify_one (C++20) | notifies at least one thread waiting on the atomic object (public member function of `std::atomic_flag`)
notify_all (C++20) | notifies all threads blocked waiting on the atomic object (public member function of `std::atomic_flag`)
atomic_flag_waitatomic_flag_wait_explicit (C++20)(C++20) | blocks the thread until notified and the flag changes (function)
atomic_flag_notify_one (C++20) | notifies a thread blocked in atomic_flag_wait (function)

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